T Rex: mighty forebear of the ... chook

[mr friendly guy]

more evidence that birds evolved from dinosaurs

T Rex: mighty forebear of the ... chook

April 13, 2007 - 1:42PM

Tiny bits of protein extracted from a 68-million-year-old dinosaur bone have given scientists the first genetic proof that the mighty Tyrannosaurus rex is a distant cousin to the modern chicken.

"It's the first molecular evidence of this link between birds and dinosaurs," said John Asara, a Harvard Medical School researcher, whose results were published in today's edition of the journal Science.

Scientists have long suspected that birds evolved from dinosaurs based on a study of dinosaur bones, but until recently, no soft tissue had survived to confirm the link.

That all changed in 2005 when Mary Higby Schweitzer of North Carolina State University reported finding soft tissue, including blood vessels and cells, in a T Rex bone dug out of sandstone from the fossil-rich Hell Creek Formation in Montana.

Schweitzer, in another study appearing in this week's issue of Science, found that extracts of T. rex bone reacted with antibodies to chicken collagen, further suggesting the presence of birdlike protein in dinosaur bones.

For his study, Asara used a highly sensitive technology called mass spectrometry to determine the chemical makeup of bone fragments provided by Schweitzer and her team.

He first had to purify the bone extract, which came in the form of a gritty brown powder that remained after minerals were extracted. Asara then broke it down into peptide fragments, little bits of proteins, isolated into the amino acid sequences that make them up.

"It was very tough to get anything," he said in a telephone interview. He wound up with seven separate strands of amino acid, five of which were a particular class of collagen, a fibrous protein found in bone.

Next, Asara had to interpret the sequences. He compared his results to collagen data from living animals. Most matched collagen from chickens, while others matched a newt and frog.

"Based on all of the genomic information we have available today, it appears these sequences are closer to birds or chickens than anything else," Asara said.

Ultimately, scientists had hoped to find genetic material that was unique to the T. rex. That was not possible with the tiny T. rex sample.

"We never found unique T. rex tags," he said.

In a similar study of mastodon bones supplied by Schweitzer, Asara had more luck.

He compared the samples to a database of existing amino acid sequences and against a theoretical set of mastodon sequences and found a total of 78 peptides, including four unique sequences.

Still, Asara said the T. rex protein sequence was useful in providing clues about the evolution of the species.

The researchers said the results may change the way that people think about fossil preservation.

"The fact that we are getting proteins is very exciting," said paleontologist Jack Horner, who dug up the T. rex in 2003 and is co-author of the paper with Schweitzer.

Horner said paleontologists will need to dig deeper for specimens that have not been corrupted by ground water and bacteria.

"I think we are going to find that many specimens are like it. It will be a matter of paleontologists getting into sites that are not necessarily easy," he said.

Reuters

[Darth Raptor]

Not surprising in the least, but it's always good to have hard evidence. Even to back up the most solid of conjectures.

The title is misleading though. Obviously, Tyrannosaurus has no living descendents. The tyrannosaur line was completely annihilated, and was also the contemporary of bona fide birds.

[Ritterin Sophia]

Why aren't we injecting this protein into frog eggs? I want a God Damned baby T-Rex for a pet!

[loomer]

Why aren't we injecting this protein into frog eggs? I want a God Damned baby T-Rex for a pet!

And then you'll flush it down the toilet and we'll end up with giant reptiles rampaging beneath the streets, eating the crocodiles and alligators.

...Actually, that sounds like a cheesy, but enjoyable Sci-Fi movie.

[Azazal]

Insert obligatory dinosaurs taste like chicken joke here

[Baal]

Insert obligatory dinosaurs taste like chicken joke here

Thats ok, If his brain was large enough the T-Rex would probably think the same of you.

[Anguirus]

Actually, I think T. rex had one of the largest brains in terms of absolute size of all the vertebrates.

It just wasn't especially big compared to the rest of his body. However, his small cousins the troodontids had fairly monstrous brains for their body size.

[The Vortex Empire]

I thought it's brain was about the size of a walnut? Though, it has been a while since I've read anything dinosaur related.

[The Original Nex]

I thought it's brain was about the size of a walnut? Though, it has been a while since I've read anything dinosaur related.

That would be Stegosaurus I believe.

[Elfdart]

This new study leads me to a question:

If dinosaurs are found to not only close relatives of birds, but ancestors as well, doesn't that actually make them birds? For example, bats are descended from insectivores like shrews, but they aren't given a new class. They are mammals. Under the Linnaean system the older name takes precedence. Wouldn't the dinosaurs be "retconned" as Aves?

[Covenant]

This new study leads me to a question:

If dinosaurs are found to not only close relatives of birds, but ancestors as well, doesn't that actually make them birds? For example, bats are descended from insectivores like shrews, but they aren't given a new class. They are mammals. Under the Linnaean system the older name takes precedence. Wouldn't the dinosaurs be "retconned" as Aves?

God, I hope so. I love the idea of T-Rex having one of those cool Cockatoo frills and singing. If I had one for a pet, I'd teach it to call itself a pretty bird.

Too bad it probably wouldn't have the vocal cords or brainpower necessary, and would just eat me. Anyone have any pertinent information on their vocal passages of dinosaurs? And, as Elfdart says, if they are this intimately related to Birds... where do we stick them on the tree?

[Surlethe]

Completely random question: "chook" is Australian slang for "chicken", right?

[loomer]

Actually, a chook is only a female chicken, a hen. Not a rooster. It's not really slang either. It seems to hover in that grey area between slang, and between fully recognized, legitimate word.

[The Original Nex]

This new study leads me to a question:

If dinosaurs are found to not only close relatives of birds, but ancestors as well, doesn't that actually make them birds? For example, bats are descended from insectivores like shrews, but they aren't given a new class. They are mammals. Under the Linnaean system the older name takes precedence. Wouldn't the dinosaurs be "retconned" as Aves?

More like the other way around. All birds are dinosaurs, but not all dinosaurs are birds. IMO, Aves should be done away with, and placed under the auspices of a new class "Dinosauria". Or perhaps break up the dinosaurs as a group, leaving Ornithischia with Reptilia, and placing Saurischia (which includes all Aves) under the auspices of a new class.

[Akhlut]

Taxonomists will probably find something suitably different between dinosaurs and birds to keep the classifications separate, like that for mammals and reptiles (wherein the only thing that separates mammals from reptiles, taxonomically speaking, is the fact that mammals have dentary-squamosal joints for their jaws and reptiles don't).

[The Original Nex]

God, I hope so. I love the idea of T-Rex having one of those cool Cockatoo frills and singing. If I had one for a pet, I'd teach it to call itself a pretty bird.

Too bad it probably wouldn't have the vocal cords or brainpower necessary, and would just eat me. Anyone have any pertinent information on their vocal passages of dinosaurs? And, as Elfdart says, if they are this intimately related to Birds... where do we stick them on the tree?

Tyrannosaurs, and all Theropod dinosaurs (of which modern birds are included), likely had feathers at some point in their life-cycle, and almost certainly as chicks. Whether the larger Theropods had decorative plumes during the mating season is all pure speculation at this point, but fossil evidence shows that many small theropods, and the Maniraptors in particular (again, including modern birds) had at least an insulatory coat of feathers throughout their life.

As far as I am aware, the vocalizations of most dinosaurs are entirely speculative. Exceptions would be the Hadrosaurines and Lambeosaurines, with some anylizing of the complex nazel cavities in the sinuses (and sinus crests) of many of these species.

Also beware of falling into the trap of grouping dinosaurs into a monolithic group. Dinosaurs are a remarkably diverse group, with two scientifically recognized Orders, Saurischia and Ornithischia. Even within these groups there is massive diversity. Saurischia contains all the Theropods, Prosauropods, and Sauropods, from tiny Microraptor, right on up to the largest Argentinosaurus. Ornithischia is further diverse, containing, the Ornithopods (Hypsilophodonts, Iguanodonts, Hadrosaurs, and more), Marginocephalians (Boneheads, and Ceratopsians) and Thyreophorans (Stegosaurs, and Ankylosaurs). To try to come up with a generalization on something specific, like vocal patterns, about the Dinosauria as a whole, is neigh impossible.

[The Original Nex]

Taxonomists will probably find something suitably different between dinosaurs and birds to keep the classifications separat

Except for the blurred areas. Many species of the so-called "non-avian" Maniraptors (gouped within the Oviraptorosauria, Therizinosauria, Deinonychosauria) are so similar to what we would consider birds, that some paleontologists consider them flightless birds, possibly descended from animals that were flight capable. Where is the line drawn.

like that for mammals and reptiles (wherein the only thing that separates mammals from reptiles, taxonomically speaking, is the fact that mammals have dentary-squamosal joints for their jaws and reptiles don't).

And hair, and lactation. Here it is the Cynodonts (the last of the "mammal-like reptiles" or the non-mammalian Synapsids), that are the gray area. Some are more reptillian, others are more mammalian. There is always gray area in Taxonomy, as it is not, and can never be, an exact science.

As far as birds and dinosaurs, there are no differences between the Theropods and Aves that are nearly as distinct as between early Synapsids and Mammals. Some would say flight is a good distinction between birds and dinosaurs, but there is evidence that some small dinosaurs were capable of flight. Where is the clear "dividing line" between dinos and birds; as lactation and hair clearly divide mammals and reptiles?

[Akhlut]

Where is the line drawn.

I'm not the one to ask for that. Dinosaurs and birds aren't my forte. However, if there is skeletal evidence of the air-sacs found near bones, I'd say those would probably be a prime candidate for differentiating between the two.

As far as birds and dinosaurs, there are no differences between the Theropods and Aves that are nearly as distinct as between early Synapsids and Mammals. Some would say flight is a good distinction between birds and dinosaurs, but there is evidence that some small dinosaurs were capable of flight. Where is the clear "dividing line" between dinos and birds; as lactation and hair clearly divide mammals and reptiles?

My apologies, I wasn't clear enough; anyway, I was talking about the mammal-like reptiles as far as differentiating between mammals and reptiles taxonomically. My mammalogy professor said that the main difference taxonomically between the mammal-like reptiles and early mammals is the fact that the mammals have a D-S joint and the reptiles don't.

[Darth Raptor]

Birds have their own class because Linneaus only examined living animals. Yeah, birds are really different from from every other kind of animal alive today, but when you examine the fossil record in its entirety it becomes clear that Aves is a bad clade to destruct. Archosauria should be a class distinct from reptiles, I don't disagree there, but it should include dinosaurs, pterosaurs, crocodiles AND birds. The distinction between lizards/snakes and archosaurs is much more clear than the distinction between dinosaurs and birds.

Imagine if something happened that wiped out nearly ever species of mammal alive today, and only left bats. The intelligent lizard people of the distant future would be inclined to consider cheiropteroids a unique class. That's essentially what's happening here.

[The Original Nex]

Where is the line drawn.

I'm not the one to ask for that. Dinosaurs and birds aren't my forte. However, if there is skeletal evidence of the air-sacs found near bones, I'd say those would probably be a prime candidate for differentiating between the two.

Most Theropods have air sacs and a bird-like pulmonary system.

As far as birds and dinosaurs, there are no differences between the Theropods and Aves that are nearly as distinct as between early Synapsids and Mammals. Some would say flight is a good distinction between birds and dinosaurs, but there is evidence that some small dinosaurs were capable of flight. Where is the clear "dividing line" between dinos and birds; as lactation and hair clearly divide mammals and reptiles?

My apologies, I wasn't clear enough; anyway, I was talking about the mammal-like reptiles as far as differentiating between mammals and reptiles taxonomically. My mammalogy professor said that the main difference taxonomically between the mammal-like reptiles and early mammals is the fact that the mammals have a D-S joint and the reptiles don't.

Does taxonomy only concern skeletal issues? Surely this is necesary in the fossile record, but I though a main trait that places one within Mammalia is hair/fur and lactation? Correct me if I'm wrong. Of course, we have no way of knowing when the Synapsids developed lactation and hair due to the lack of trace of such features in fossils. In any case, some later Therapsids had the D-S Joint.

As it is, we are arguing semantics, taxonomy is not precise, particularly in the fossil record, but also overall, as so-called "transitory species" that have traits from two different clades are difficult to place on a cladogram.

[The Original Nex]

Birds have their own class because Linneaus only examined living animals. Yeah, birds are really different from from every other kind of animal alive today, but when you examine the fossil record in its entirety it becomes clear that Aves is a bad clade to destruct. Archosauria should be a class distinct from reptiles, I don't disagree there, but it should include dinosaurs, pterosaurs, crocodiles AND birds. The distinction between lizards/snakes and archosaurs is much more clear than the distinction between dinosaurs and birds.

Imagine if something happened that wiped out nearly ever species of mammal alive today, and only left bats. The intelligent lizard people of the distant future would be inclined to consider cheiropteroids a unique class. That's essentially what's happening here.

I agree. Although the issue of warm-bloodedness in at least (most?) Theropods and birds always makes me hesitate on how they should be grouped with the Archosaurs, including the other dinosaurs. Warm-bloodedness is a pretty distinct evolutionary trait.

[Darth Raptor]

It's pretty much a given that ALL dinosaurs- not just theropods- were endothermic. Pterosaurs HAD to be, they're impossible otherwise. And pterosaurs diverged earlier than theropods. So either the archosaurs have developed warm-bloodedness twice or the cutoff is anything more advanced than a crocodile. Interestingly, crocodiles already have most of the necessary hardware (an advanced heart that distinguishes them from lizards).

[The Original Nex]

It's pretty much a given that ALL dinosaurs- not just theropods- were endothermic. Pterosaurs HAD to be, they're impossible otherwise. And pterosaurs diverged earlier than theropods. So either the archosaurs have developed warm-bloodedness twice or the cutoff is anything more advanced than a crocodile. Interestingly, crocodiles already have most of the necessary hardware (an advanced heart that distinguishes them from lizards).

Interesting. What are some ideas on how Sauropods coped with being endothermic, the issue being radiating heat despite their great mass and food consumption?

I would indeed like to see the clades reorganized, with the archosaurs and their kin placed into an Archosauria class as you suggest. Unfortunately, I feel that, while taxonomy can rapidly on family and genera levels, taxonomists would be far more conservative and slow to change and reorganize the established Reptilia and Aves classes. Hopefully someday.

[Elfdart]

Birds have their own class because Linneaus only examined living animals. Yeah, birds are really different from from every other kind of animal alive today, but when you examine the fossil record in its entirety it becomes clear that Aves is a bad clade to destruct. Archosauria should be a class distinct from reptiles, I don't disagree there, but it should include dinosaurs, pterosaurs, crocodiles AND birds. The distinction between lizards/snakes and archosaurs is much more clear than the distinction between dinosaurs and birds.

Imagine if something happened that wiped out nearly ever species of mammal alive today, and only left bats. The intelligent lizard people of the distant future would be inclined to consider cheiropteroids a unique class. That's essentially what's happening here.

But once they found remains of shrews and moles and other mammals and put two and two together, then there's no logical reason to put them in different classes. Either the older class name is used (under the Linnaean System, the older name has more clout) or the bats would be submerged into a new class including the other critters, i.e. Mammals.

I should think that a new class name is in order, elevating Archosauria to a class and making Aves an order. If not, then the dinosaurs belong under Aves.

[The Original Nex]

I should think that a new class name is in order, elevating Archosauria to a class and making Aves an order. If not, then the dinosaurs belong under Aves.

The former makes far more sense than the latter. Not all dinosaurs have the traits that makes a bird a bird. Surely Apatosaurus, Triceratops, or Stegosaurus should not be considered birds. Although, I don't think Aves would be an Order. If Archosauria is elevated to a Class, then Saurischia would likely become a Superorder, with Aves being between that Superorder, and the multitude of avian Orders. Unless the avian Orders are lowered to Infraorder status, while Aves becomes the Order of all birds, something I see unlikely.